<template>
  <div class="star" :class="'star-'+size">
    <span class="star-item" v-for="(sc, index) in starClasses" :class="sc" :key="index"></span>
  </div>
</template>
<script>
// 类名常量
const CLASS_ON = "on";
const CLASS_HALF = "half";
const CLASS_OFF = "off";
export default {
  props: {
    score: Number,
    size: Number
  },
  computed: {
    /*
    3.2: 3 + 0 + 2
    4.7: 4 + 1 + 0
    */
    // 该方法产生一个数组starArr来表示on half off类名的span数量（总长度为5）
    starClasses() {
      const { score } = this;
      const starArr = [];
      // 向starArr中添加n个CLASS_ON
      const scoreInteger = Math.floor(score);
      for (let i = 0; i < scoreInteger; i++) {
        starArr.push(CLASS_ON);
      }
      // 向starArr中添加0/1个CLASS_HALF
      if (score * 10 - scoreInteger * 10 >= 5) {
        starArr.push(CLASS_HALF);
      }
      // 向starArr中添加n个CLASS_OFF
      while (starArr.length < 5) {
        starArr.push(CLASS_OFF);
      }
      return starArr;
    }
  }
};
</script>
<style lang="stylus" rel="stylesheet/stylus">
.star {
  float: left;
  font-size: 0;

  .star-item {
    display: inline-block;
    background-repeat: no-repeat;
  }

  &.star-48 {
    .star-item {
      width: 20px;
      height: 20px;
      margin-right: 22px;
      background-size: 20px 20px;

      &:last-child {
        margin-right: 0;
      }

      &.on {
        bg-image('./images/star48_on');
      }

      &.half {
        bg-image('./images/star48_half');
      }

      &.off {
        bg-image('./images/star48_off');
      }
    }
  }

  &.star-36 {
    .star-item {
      width: 15px;
      height: 15px;
      margin-right: 6px;
      background-size: 15px 15px;

      &:last-child {
        margin-right: 0;
      }

      &.on {
        bg-image('./images/star36_on');
      }

      &.half {
        bg-image('./images/star36_half');
      }

      &.off {
        bg-image('./images/star36_off');
      }
    }
  }

  &.star-24 {
    .star-item {
      width: 10px;
      height: 10px;
      margin-right: 3px;
      background-size: 10px 10px;

      &:last-child {
        margin-right: 0;
      }

      &.on {
        bg-image('./images/star24_on');
      }

      &.half {
        bg-image('./images/star24_half');
      }

      &.off {
        bg-image('./images/star24_off');
      }
    }
  }
}
</style>
